From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Analysis of hydraulic damper performance, discussing piston leakage, valve timing, cushioning, and axle loads.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 150 | |
| Date | 1st April 1927 guessed | |
| contd :- -3- will prefer to leak past the main piston. It will be seen from Graph 1. WHERE we have the ball end load against the piston velocity obtained as described later, that with the normal front axle loading the piston travels 10% to 15% of its total stroke before the high pressure valve lifts and that the H.P. valve closes 3 or 4% before the end of the piston travel. We therefore conclude that 3 or 4% of the piston travel under the particular conditions of that test provides the cushion which is partially due to compressing the emulsion of oil and air and partially due to leakage past the main piston. The remainder of the 10-15% is conceivably partially lost movement occasioned by the fact that the enormous viscosity loads produced by violent axle movements of over 400 lbs/sq.in., force an appreciable quantity of oil past the piston, and in consequence the replenishing ball valves working under atmospheric pressure only, cannot entirely replace the quantity lost in the short time available. As the load on the high pressure valve is increased, so the % of the stroke which elapses before the H.P. valve opens, increases, in other words on the rear there is more cushioning for a given ball pin load than on the front due to :- (a) The higher cyl. pressures used to obtain this ball pin load. (b) The multiplication at the axle of any cushioned movement of the piston due to the longer lever employed at the rear. This confirms the impression that we have always had of the hydraulics on the rear. They are very effective over humped back bridges or other as obstacles promoting large axle movements, but they contd :- | ||